Cooling device for cooling medium-voltage switchgear by means of live heat pipes

ABSTRACT

A cooling device including an evaporator operating with a phase-change heat-transfer fluid surrounding electrical switchgear operating at high voltage and connected to one or more condensers placed on a roof of a sheath in which the electrical switchgear is placed. The condensers are supported in this location by insulating elements that include side partitions that are to the side relative to a box, placed above the sheath and/or a central portion of the roof of the sheath. The cooling device consumes very little energy and does not require an electrically insulated cooling system to be designed and can be used, for example, for application to medium-voltage generator circuit breakers.

FIELD OF THE INVENTION

The invention relates in particular to the field of circuit breakers or disconnectors for medium-voltage generators, placed in a protective sheath, and using cooling devices called “heat pipes” that operate with a phase-change heat-transfer fluid.

PRIOR ART AND PROBLEM POSED

The constant concern of makers of that type of equipment is to increase the ability of such gear to conduct higher and higher currents, in particular for circuit breakers and disconnectors placed inside busbars at the outlets of power stations for producing or distributing electricity. That applies particularly for alternator circuit breakers.

A method that is generally used consists in making more uniform the temperature of the air that is in contact with the various heating and heated parts of the circuit breaker concerned. The cooling inside such a protective sheath may take place by natural or forced convection of the air enclosed therein and in which the circuit breaker is to be found, the prevailing temperature inside the protective sheath being considerably higher than the prevailing temperature outside, by 30° C. to at least 40° C. However, the use of such auxiliary gear, such as ventilators, presents various drawbacks, which are: high electricity consumption on the main circuit, risk of losing auxiliary ventilators and consequently the need for duplicating them or for providing for degraded operating modes, noise, and considerable bulkiness. Another solution consists in providing an increase in the current flow section in the various transmission elements, and thus increasing the size of circuit breaker parts.

Patent document EP 1 657 731 describes a known cooling device and method for cooling a high-voltage disconnector or a circuit breaker. FIG. 1 shows, in section, an embodiment described in that document. FIG. 1 mainly shows a high-voltage conductor or the casing of a circuit breaker. It is surrounded by evaporators 3 forming part of a cooling assembly 1 therefor. Such an assembly is accompanied by an insulating sleeve 7 surrounding a device operating with a phase-change heat-transfer fluid 5 in order to evacuate the heat collected by the evaporators 3. A flexible sleeve 9 completes the assembly. The various parts are placed together inside a protective sheath 8. The cooling assembly opens out to the top of this protective sheath 8 leading to a condensation device 4, e.g. with fins.

The object of the invention is to propose a different solution for cooling switchgear.

SUMMARY OF THE INVENTION

To this end, the invention mainly provides a cooling device for cooling medium-voltage switchgear placed inside a protective sheath, in order to evacuate a portion of the heat delivered by the switchgear, the device comprising:

evaporators operating with a phase-change heat-transfer fluid, and being placed around the casing of the switchgear;

condensers placed above the protective sheath; and

a box surrounding the top of the assembly,

According to the invention, the evaporators and the condensers are in electrical contact with the medium-voltage switchgear, and insulating parts are used for insulating the condensers relative to the roof of the sheath and to the box.

In a preferred embodiment, the insulating parts, relative to the roof of the protective sheath, are constituted by a central portion of the roof of the protective sheath and on which the condensers rest.

In this preferred embodiment, side partitions are used for channeling the streams of air reaching the condensers from the side.

In a particular embodiment of the device of the invention, side ventilation means may be added to the device.

LIST OF FIGURES

The invention and its various technical characteristics can be better understood on reading the following description, accompanied by several figures in which, respectively:

FIG. 1, described above, is a cross-section showing a prior art cooling system for medium-voltage gear, using elements operating with a phase-change fluid;

FIG. 2 is a cross-section showing a first embodiment of the device of the invention;

FIG. 3 is a cross-section showing a second embodiment of the device of the invention; and

FIG. 4 is a longitudinal section of both of the embodiments of the device of the invention shown in FIGS. 2 and 3.

DETAILED DESCRIPTION OF TWO EMBODIMENTS OF THE INVENTION

With reference to FIG. 2, a sheath 15 contains, for example, switchgear, such as a circuit breaker 10, or a busbar section isolator, forming part of a high-voltage electricity transmission installation. Double-walled evaporators 11 containing a phase-change heat-transfer fluid, surround the outside wall of the circuit breaker 10. This circuit breaker 10 and its evaporators 11 form a live assembly 12 and they are supported on the inside of the sheath 15 by an insulating support 18.

The top portion of the evaporators 11 is connected to at least one pipe 14 that passes through the roof 16 of the sheath 15. Each pipe 14 leads to a condenser 21, which is placed on the roof 16 of the sheath 15. The condenser(s) 21 are themselves placed inside a box 20, which is placed above the sheath 15, and they are subjected to a flow of air, in particular passing through side walls 22 having air passages and through a top space 25 of the box 20, the space being just below the roof 16 of the box.

Thus, the evaporators 11 operate with a phase-change heat-transfer fluid, installed along the walls of the circuit breaker casing, and possibly the disconnector casing, evacuating a portion of the heat of the casing, which is at a temperature of 100° C. These evaporators 11 therefore transmit the heat by means of the pipe 14 to the condenser 21, which is placed above the sheath. It should be remembered that the evaporators 11, the pipes 14, and the condensers 21 are in electrical contact with the circuit breaker 10. Thus, it is no longer necessary to consider insulating them electrically relative to the circuit breaker.

Just like the live assembly 12 composed of the circuit breaker 10, the evaporators 11, the pipes 14 and the condensers 21, which is insulated relative to the sheath 15, provision is made for the condensers 21 also to be insulated relative to the roof 16 of the sheath 15 and to the box 20 and in particular to the side walls 22 thereof. To do this, the roof 16 of the sheath 15 includes an insulating central portion 17, which central portion fills in a gap between two side portions 19 of the roof and supports the condensers 21. In addition, side partitions 24 are provided on either side of the condensers 21 extending to the side walls 22 of the box 20, in order to channel the streams of air reaching the condensers 21 from the side. These supporting side partitions are made from insulating material. Thus, the various cooling elements of the circuit breaker 10 are electrically insulated relative to the infrastructure in which they are placed.

It should be noted that the evaporators 11 that surround the walls of the circuit breaker 10 casing, may similarly be replaced by reservoirs on its surface, possibly comprising a plurality of reservoir parts.

In FIG. 2, the condensers 21 are cooled by natural convection.

FIG. 3 shows an installation that is similar, apart from side ventilation means 26 that are provided on the outside of the box 20, and more specifically facing the side walls 22. Thus, the cooling of the condensers 21 is no longer ensured by natural convection but by forced convection.

FIG. 4 is a longitudinal section showing the installations, as shown in FIGS. 2 and 3. FIG. 4 shows a circuit breaker 10 that is placed on an insulating support 18 and enclosed inside a sheath 15. Said circuit breaker 10 forms part of a set of switchgear for handling and transporting electricity at medium voltage, and it also benefits from the cooling system of the invention, by being surrounded by evaporators 11. FIG. 4 shows a plurality of pipes 14, each pipe ending in a condenser 21 that is placed on the insulating central portion 17 of the roof of the sheath 15. The arrows show longitudinal and horizontal flows of air, entering through the right and left ends and exiting through the top portion of the box 20.

The advantages of the device of the invention are that it does not consume energy and that its development and implementation do not require an insulating cooling system to be designed, thereby saving time when developing such an installation. 

1-4. (canceled)
 5. A cooling device for cooling medium-voltage switchgear placed inside a sheath, comprising: evaporators operating with a phase-change heat-transfer fluid, and placed about a casing of the switchgear; condensers placed above the sheath; and a box surrounding a top of the assembly, wherein the evaporators and the condensers are in electrical contact with the medium-voltage switchgear, and insulating parts are provided for insulating the condensers relative to a roof of the sheath and to the box.
 6. A device according to claim 5, wherein the insulating parts include a central portion of the roof of the sheath for insulating the condensers relative to the roof of the sheath and on which they rest.
 7. A device according to claim 5, further comprising side partitions for channeling streams of air reaching the condensers of the box from the side.
 8. A device according to claim 6, further comprising side partitions for channeling streams of air reaching the condensers of the box from the side.
 9. A device according to claim 5, further comprising side ventilation means, which are placed outside the box, facing the side walls of the box. 